Dual layered or multi-layered cosmetic compositions have become popular over the years, because of their appealing appearance. Such compositions have been developed for applications in skin care and hair care. Multi-layered liquid products in other fields are also known. In some multi-layered products, one liquid layer is incompatible with one or more other liquid layers. By “incompatible”, we mean that the layers are mutually insoluble and mutually non-reactive. Because of this, the less dense layers tend to sit on top of the more dense layers. We consider such a product “stable” if the layer separation can be maintained for a defined period of time, and if the interface between two layers is no thicker than a specified thickness. The separated layers may be mixed within each other prior to use, by shaking the composition. Depending on the composition, a typical consumer product may take several seconds or several minutes of shaking to form a homogenous mixture of the layers. In part, it depends on the viscosity of the layers, and the size and shape of the container. After shaking, in order to maintain the mixed state temporarily, (i.e. during consumer use), some products use surfactant. But if too much surfactant is used, the layers will take too long to separate.
Other multi-layered products may use certain agents that are able to maintain separation of two or more layers that might otherwise mix. For example, some existing multi-layered (two or more layers) cosmetic compositions use emulsifiers and/or salts to achieve and/or maintain a stable multi-layered system. However, emulsifiers, surfactants, and salts can be irritating or harmful to the user if their concentration is too high. For example, U.S. Pat. No. 7,988,981 teaches 8-18% of water soluble salts as a necessary component of a multi-layered cosmetic composition. This is unlike the present invention which has no more than about 1% salt content, and typically much less. '981 implies that such a low concentration of salt would be insufficient to achieve layer separation (see column 2, lines 57-63). Nevertheless, the present invention achieves clean layer separation, even by going against the teaching of '981. The '981 patent also claims compositions having mineral oil. However, some consumers have developed a negative perception of mineral oils in cosmetics. In contrast, the present invention may comprise no more than about 1% mineral oil.
Furthermore, with repeated mixing of a composition during regular use, some existing multi-layered systems can take longer and longer to return to a stable, separated state, and the product becomes less appealing over time. This is unlike the present invention.
Natural oils have been used for centuries to condition human hair, but when used alone, they can impart a stickiness that is undesirable and unappealing to the user. Silicones have been used in hair care to provide a silky and smooth feel, but can leave an unnatural shine behind. To mitigate these problems, hydrophilic ingredients may be used. In that case, emulsifiers have often been used to combine oils, silicones and hydrophilic materials into an emulsion. However, emulsions do not have the appeal of well executed multi-layered compositions. As such, there is a need for stable, multi-layered compositions comprising natural oils, silicones, and hydrophilic ingredients without substantial amounts of surfactants and emulsifiers. Furthermore, it is desirable to incorporate into a multi-layered composition, ingredients that are beneficial to hair care, such as novel combinations of certain essential oils and various hydrophilic ingredients.